The present invention relates to a fiber reinforced rubber, particularly, a reinforcement embedded in a rubber.
Since high tensile strength, high elasticity, high dimensional stability, and high adhesive strength has been required for rubbers such as a belt, a tire, and a hose, a reinforcing cord constructed by fibers or a reinforcing canvas is embedded in a rubber. Generally, a cord of twisted yarns is used for the reinforcement. The yarn may be all twisted, only half of them twisted, or lang lay. The yarns, all of them twisted, are most popular for reinforcement for a rubber.
However, monofilaments rub each other with sharp angles in a part of the rubber which is reinforced by all of the twisted yarn and accordingly, the yarn is worn out, broken, or decreased in tensile strength from the rubbed parts thereof after a short period of usage. Therefore, the flex fatigue is lowered.
Japanese Patent Application Laid Open Gazette No. 59-19744 proposed a fiber reinforced rubber, which reinforcement is constructed by cords in which half of the yarns are twisted, or a lang lay to solve the above problems (flex fatigue).
However, a rubber reinforced by cords of only half yarns are twisted or the lang lay is lowered in elongation and the rate of the tensile elasticity after the dipping process, compared with a rubber reinforced by cords in which all yarns are twisted. This results in a lower dimensional stability.
On the other hand, a braided cord has been made for various purposes. A cylindrically braided cord which needs more than four and even numbered yarns to make a cylindrical configuration surpasses a twisted cord in flex fatigue and dimensional stability due to its constructional characteristics. Therefore, a cylindrically braided cord will improve both the flex fatigue resistance and dimensional stability when used for the reinforcement of rubber.
Moreover, in case that the cylindrically braided cord is used for the reinforcement of a rubber, if the yarns constructing the cord are twisted, the cord is arranged orderly and consequently, a higher strength of the cylindrically braided cord and a longer service life of the rubber is expected. If in all the yarns, the right twist oriented and the left twist oriented, are twisted in the same direction, the cylindrically braided cord may possess a direction and rubber reinforced by such a cylindrically braided cord possessing such a direction may not obtain satisfactory results in flex fatigue resistance.